JPH1067577A - Production of porous material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a porous material, readily moldable into a complicated shape and having continuous pores without lowering a baking temperature and without deteriorating the strength. SOLUTION: An inorganic molding powder is mixed with a cross-linkable compound and an uncross-linkable compound which is compatible with the cross-linkable compound or flowable, and the resultant mixture is then molded into a prescribed shape. The cross-linkable compound is cross-linked and converted into a polymer around the periphery of the powder to afford a cured product of a prescribed shape. The uncross-linkable compound is kept at a temperature of the solidifying temperature or below to promote the solidification and growth and the uncross-linkable compound is volatilized and removed to form continuous pores. Thereby, the continuous pores of the cured product are not reduced by the uncross-linkable compound even without lowering the baking temperature, and the porous material of a complicated shape having the continuous pores can be molded while providing a high strength by baking at a prescribed temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous body, and more particularly to a method for producing an inorganic porous body having high strength and continuous pores in a complicated shape.

[0002]

2. Description of the Related Art As a method for producing an inorganic porous material, which is being used for a ceramic filter or the like, the range of use of which is being expanded, ceramic powder is filled in a mold or the like, and then molded.
In the case of firing, lower the firing temperature to reduce the degree of densification so as to utilize the particle gap formed, or mix ceramics powder with an organic substance in a slurry form, fill it into a mold, etc. and mold it, Degreasing and baking are performed to eliminate organic matter in the molded body and use it as pores.

[0003]

However, in the method of obtaining a porous body by lowering the firing temperature, in order to increase the number of continuous pores, it is necessary to fire at a lower temperature. There is a problem that the strength of the porous body itself is significantly reduced.

[0004] In particular, when the filter is used as a ceramic filter, if the filter is made thinner in order to increase the filter area, there is a problem that the strength is further reduced and the filter cannot be put to practical use.

[0005] Further, there is a contradictory problem that an attempt to improve the strength of a molded article remarkably reduces continuous pores.

On the other hand, in a method in which an organic substance is mixed in a ceramic powder and traces of the organic substance after firing are used as pores, if continuous pores are to be formed, continuous fibers are put into a slurry. It is conceivable to form the molded article by eliminating the carbon fiber. However, when trying to produce a molded article having a complicated shape, there is a problem that the arrangement of the continuous fibers is difficult, and the molding is extremely difficult.

The present invention has been made in view of the above prior art, and is intended to produce a porous body having continuous pores which can be easily formed into a complicated shape without lowering the firing temperature and lowering the strength. It seeks to provide a way.

[0008]

According to a first aspect of the present invention, there is provided a method for producing a porous body, comprising: a step of producing an inorganic porous body having continuous pores; The body is mixed with a cross-linkable compound and a non-cross-linkable compound that is compatible with the cross-linkable compound or imparts fluidity, and is molded into a predetermined shape. Simultaneously with the molecularization, the non-crosslinkable compound is kept below the freezing point and solidified so as to be continuous between the polymerized crosslinkable compounds, and then the solidified non-crosslinkable compound is volatilized and removed. It is assumed that.

According to this method for producing a porous body, a crosslinkable compound and a compatible or fluid non-crosslinkable compound are mixed with a powder of an inorganic material and molded into a predetermined shape. A cured product of a predetermined shape can be obtained by the compound being crosslinked and polymerized around the powder, and the non-crosslinkable compound is brought to a solidification point or lower to promote solidification growth, which is volatilized and removed to form continuous pores. Will be able to do it.

As a result, the cured product does not have reduced continuous pores due to the non-crosslinkable compound without lowering the firing temperature, and has continuous pores while maintaining high strength by firing at a predetermined temperature. Complex shapes can be formed.

According to a second aspect of the present invention, there is provided a method for manufacturing a porous body, wherein the non-crosslinkable compound is expanded with water which has been solidified as water. To form continuous pores.

According to this method for producing a porous body, water is used as the non-crosslinkable compound, and the water mixed with the inorganic powder and the crosslinkable compound is frozen below the freezing point to freeze the polymer. The expanded portion is expanded so that continuous pores can be easily formed.

Further, the method for producing a porous body according to the third aspect of the present invention provides the method according to the first or second aspect,
The diameter of continuous pores is controlled by adjusting the degree of progress of crosslinking of the crosslinkable compound around the powder and solidification growth of the non-crosslinkable compound.

According to the method for producing a porous body, the progress of the crosslinking of the crosslinkable compound and the degree of solidification growth of the non-crosslinkable compound around the powder are adjusted, and the progress of the crosslinking is promoted to thereby form the continuous pores. The diameter can be reduced, and the coagulation of the non-crosslinkable compound can be promoted to increase the diameter of the continuous pores.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for producing a porous body of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a process chart according to an embodiment of the method for producing a porous body of the present invention.

In this method for producing a porous body, the inorganic porous body 10 having continuous pores is produced, and is suitable for producing, for example, a ceramic filter.

(1) As the porous body 10, an inorganic powder is used as the molding powder 11, and for example, alumina powder or partially stabilized zirconia powder is used.

A crosslinkable compound 12 and a non-crosslinkable compound 13 are mixed with the inorganic powder molding powder 11 to form a molding material.

The crosslinkable compound 12 is used to cure the molding powder 11 by forming a crosslinked polymer around the molding powder 11 as a nucleus. For example, urea resin, melamine resin, maleic resin, urethane resin Resins, furan resins, unsaturated polyester resins, phenol resins, diallyl phthalate resins, epoxy resins, guanamine resins, and the like are used.

The crosslinking compound 12 is used by adding a curing agent according to the type of each crosslinking compound as required.

The molding powder 11 and the crosslinkable compound 1
Non-crosslinkable compound 13 mixed in 2
A non-crosslinkable compound compatible with No. 2 or a non-crosslinkable compound capable of uniformly dispersing the crosslinkable compound 12 to give fluidity is used. Is attached to the portion where the continuous pores 14 are to be formed between the crosslinkable compounds 12 without being crosslinked.

As the non-crosslinkable compound 13, for example, water is used. In the case of water, when the freezing point is kept below the freezing point and the mixture is frozen, it expands. It is suitable for forming the continuous pores 14 by expanding them.

As described above, the crosslinking powder 1 is added to the molding powder 11.
2 and the non-crosslinkable compound 13 are mixed, and the mixing ratio thereof is such that the crosslinkable compound 12 is 1 to 50 of the molding powder 11.
% By weight, and the non-crosslinkable compound 13 is 1% by weight or more.

When the amount of the crosslinkable compound 12 is less than 1% by weight, the shape retention of the cured product after the crosslinkable compound 12 is polymerized becomes insufficient, and the strength of the non-crosslinkable compound 13 with respect to coagulation is also insufficient. This is sufficient, and cracks and the like are likely to occur.

On the other hand, if the amount of the crosslinkable compound 12 exceeds 50% by weight, the crosslinkable compound 12 will be cracked during degreasing by heating.

When the amount of the non-crosslinkable compound 13 is less than 1% by weight, the solidification and growth of the non-crosslinkable compound 13 become insufficient, and the formation of the continuous pores 14 becomes difficult.

(2) The molding powder 11 is mixed with a crosslinkable compound 12 and a non-crosslinkable compound 13, and a dispersant and a curing agent added as necessary to form a molding material. It is filled in a mold having a predetermined shape, and is cured by crosslinking the crosslinkable compound 12 into a polymer.

The filling of the mold may be performed, for example, in a state where the mold is heated so that curing can be promoted.

Then, the cured product of the molding material filled and cured in the molding die is released from the molding die.

(3) In the demolded cured product, as shown schematically in FIG.
Each of the particles 1 is used as a nucleus to form a crosslinked polymer. The cured product is kept below the freezing point of the non-crosslinkable compound 13 to promote the crystal growth of the non-crosslinkable compound 13 located between the crosslinkable compounds 12.

Then, the non-crosslinkable compound 13 is continuously solidified between the crosslinkable compound 12 which has been crosslinked around the inorganic molding powder 11 and polymerized.

When the cured product is kept at a temperature below the freezing point of the non-crosslinkable compound 13, if the cured product is given a temperature gradient so that the crystal growth has a directivity, the non-crosslinkable compound 13 is more reliably formed. The compound 13 can be continuously coagulated between the crosslinkable compounds 13.

(4) Next, the solidified non-crosslinkable compound 1
By volatilizing and removing only 3, the portion of the non-crosslinkable compound 13 is made into continuous pores 14.

For this reason, the cured product is returned to a temperature higher than the freezing point such as room temperature, and only the non-crosslinkable compound 13 is volatilized and removed.

As a result, as shown schematically in FIG. 3, the crosslinked compound 1 is formed around the inorganic molding powder 11.
The space from which the non-crosslinkable compound 13 has been removed is formed as the continuous pores 14 between the portions where the polymer 2 has adhered and the polymer has been crosslinked.

(5) Thereafter, the cured product having the continuous pores 14 formed therein is removed by volatilizing the crosslinkable compound 12 around the inorganic powder 11 and then sintering at a sintering temperature. Thus, the porous body 10 having continuous pores is obtained.

The porous body 10 having continuous pores thus obtained
Since the sintering is performed in a state in which the continuous pores 14 are formed in advance, the continuous pores 14 do not decrease without lowering the sintering temperature, and sinter at a predetermined sintering temperature to achieve high strength. And the continuous pores 14 can be formed.

Further, by changing the molding die, the porous body 10 having continuous pores having a complicated shape can be easily molded.

Further, the crosslinked polymer of the crosslinkable compound 12 in the molding material is filled and molded into a molding die, so that the demolded cured product becomes strong and does not break even when touched by hand. It can provide excellent shape retention.

Further, the diameter of the continuous pores 14 can be controlled by the degree of cross-linking of the cross-linkable compound 12 and the degree of solidification and growth of the non-cross-linkable compound 13 in the molding material. By promoting this, the diameter of the continuous pores 14 can be reduced, and by promoting the solidification of the non-crosslinkable compound 13, the continuous pores 1 can be reduced.
4 can be increased in diameter.

Further, by changing the mixing ratio of the crosslinkable compound 12 and the non-crosslinkable compound 13 to the inorganic molding powder 11, the porosity of the porous body 10 of the continuous pores 14 (total volume of the porous body) (The ratio of the volume of the pores to the pores) can be adjusted and controlled, and the porosity can be increased by increasing the mixing ratio of the non-crosslinkable compound 13.

[0043]

【Example】

(Example 1) 100% by weight of partially stabilized zirconia powder as a molding powder, 7% by weight of an epoxy resin (aliphatic) as a crosslinkable compound, 25% by weight of water as a non-crosslinkable compound, and xylene as a curing agent 1.5% by weight of a diamine and 1.5% by weight of a dispersant were prepared.

After the partially stabilized zirconia powder, dispersant, epoxy resin (aliphatic) and water were wet-mixed in a ball mill, a curing agent was added to obtain a molding material.

This molding material was poured into a casting mold heated to 70 ° C. under normal pressure and cured for about 30 minutes.

Thereafter, the cured product was removed from the casting mold at room temperature. The cured product thus obtained was very strong, and had sufficient shape retention even when touched by hand.

Further, the cured product was kept in an atmosphere at -5 ° C. for 24 hours to promote the cross-linking of the epoxy resin and the coagulation growth of water.

Thereafter, the temperature was returned to normal temperature to obtain a cured product from which water was volatilized and removed. In this cured product, continuous fine pores having a diameter of 5 μm were observed, and no crack was generated in the cured product itself.

The cured product in which the continuous pores were formed was sintered after elevating the temperature from room temperature to 600 ° C. at 5 to 15 ° C./min in order to volatilize and decompose the epoxy resin. The sintered porous body thus obtained had no cracks and had a porosity of 45%.

(Example 2) 100% by weight of alumina powder as a molding powder, 5% by weight of diallyl phthalate prepolymer as a crosslinkable compound, 30% by weight of water as a non-crosslinkable compound, and 1.5% by weight of a dispersant Prepared.

These alumina powder, dispersant, diallyl phthalate prepolymer and water were wet-mixed with a disperser to form a slurry, and a crosslinking catalyst (organic peroxide) was added to obtain a molding material.

This molding material was heated to 70.degree.
It was poured into a 0 × 10 mm casting mold at normal pressure and cured for about 30 minutes.

Thereafter, the mold was released from the casting mold at room temperature to obtain a cured product. The cured product thus obtained was very strong, and had sufficient shape retention even when touched by hand.

Further, this cured product was kept in a container inclined at a temperature from -20 ° C. to 0 ° C. for 24 hours to promote the cross-linking of the epoxy resin into a polymer and promote the solidification and growth of water in the direction of the temperature gradient.

Thereafter, the temperature was returned to normal temperature to obtain a cured product from which water was volatilized and removed. In the cured product, continuous fine pores having a diameter of 10 μm were observed to be formed in the temperature gradient direction, and no crack was generated in the cured product itself.

The cured product in which the continuous pores are formed is used to volatilize and decompose the diallyl phthalate prepolymer.
After the temperature was raised from room temperature to 600 ° C. at 5 to 15 ° C./min, sintering was performed.

The sintered porous body thus obtained includes:
No cracking occurred, and the porosity was 52%.

(Comparative Example) As a comparative example, a porous body was molded by using a molding powder in which the proportion of water as a non-crosslinkable compound was reduced in comparison with Example 1.

100% by weight of partially stabilized zirconia powder as a molding powder, 35% by weight of an epoxy resin (aliphatic) as a crosslinkable compound, and 0.1% of water as a non-crosslinkable compound.
6. 5% by weight and xylenediamine as curing agent.
5% by weight and further 2% by weight of a dispersant were prepared.

After the partially stabilized zirconia powder, dispersant, epoxy resin (aliphatic) and water were wet-mixed in a ball mill, a curing agent was added to form a molding material. After casting into a mold, the mold was removed from the casting mold, kept in an atmosphere at -5 ° C for 24 hours, and then returned to room temperature to obtain a cured product in which water was volatilized and removed. Only the pores were intermittently observed in the cured product thus obtained.

[0061]

According to the method for manufacturing a porous body according to the first aspect of the present invention, as described above in detail with one embodiment, the inorganic material powder is compatible with the crosslinkable compound or Since the fluid non-crosslinkable compound is mixed and molded into a predetermined shape, the crosslinkable compound is crosslinked and polymerized around the powder, so that a cured product of the predetermined shape is obtained, and the non-crosslinkable compound is formed. By setting the compound below the freezing point, solidification growth is promoted, and this is volatilized and removed to form continuous pores.

As a result, the cured product does not decrease continuous pores due to the non-crosslinkable compound without lowering the firing temperature, and has continuous pores while increasing the strength by firing at a predetermined temperature. A porous body having a complicated shape can be formed.

According to the method for producing a porous body according to the second aspect of the present invention, water is used as the non-crosslinkable compound. By freezing, the cross-linked polymerized portion can be expanded to form continuous pores easily and reliably.

Further, according to the method for producing a porous body according to the third aspect of the present invention, by controlling the progress of the crosslinking of the crosslinkable compound around the powder and the degree of solidification growth of the non-crosslinkable compound, The diameter of the continuous pores can be reduced by promoting the progress of crosslinking, and the diameter of the continuous pores can be increased by promoting the solidification of the non-crosslinkable compound.

[Brief description of the drawings]

FIG. 1 is a process chart according to an embodiment of a method for producing a porous body of the present invention.

FIG. 2 is an explanatory view schematically showing a crosslinked polymer of a crosslinkable compound and a solidified growth state of a non-crosslinkable compound according to an embodiment of the method for producing a porous body of the present invention.

FIG. 3 is an explanatory view schematically showing a state in which a non-crosslinkable compound according to one embodiment of the method for producing a porous body of the present invention is volatilized and removed.

[Explanation of symbols]

 Reference Signs List 10 Porous body having continuous pores 11 Molding powder 12 Crosslinkable compound 13 Non-crosslinkable compound 14 Continuous pore

Claims (3)

[Claims] 1. A method for producing an inorganic porous material having continuous pores, wherein a crosslinkable compound and a non-crosslinkable compound having compatibility with or imparting fluidity to a powder made of an inorganic material are provided. And after molding into a predetermined shape, the crosslinkable compound is crosslinked and polymerized around the powder, and at the same time, the non-crosslinkable compound is kept below the freezing point and continuously between the polymerized crosslinkable compounds. A method for producing a porous body, wherein the solidified non-crosslinkable compound is volatilized and removed. 2. The production of a porous body according to claim 1, wherein said cross-linkable compound is pushed and expanded with ice solidified with said non-cross-linkable compound as water to form continuous pores. Method. 3. The diameter of continuous pores is controlled by adjusting the degree of progress of crosslinking of the crosslinkable compound around the powder and the degree of solidification growth of the non-crosslinkable compound. The method for producing a porous body according to claim 1.